Embryonic testicular regression (Vanishing testis syndrome)


  • A developmental anomaly in which one or both testicles vanish during embryogenesis in patients with XY karyotype

Clinical features


  • Usually sporadic with rare familial instances with recessive trait

  • Unclear etiology, possibly regression of the testes in utero due to a genetic mutation, a teratogen, intrinsic gonadal disorders, infection, trauma, late antenatal or perinatal vascular thrombosis, torsion, or prenatal hormone induced atrophy resulting from overproduction of androgens

  • Incidence of monorchidism: 1/5000 males; 4.5% in patients with cryptorchidism; 40% when the testis is impalpable on physical examination

  • Incidence of bilateral anorchidism: 1/20,000 males

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